Technical Field
The disclosure relates to capacitor structures, and more particularly, to metal-insulator-metal (MIM) capacitor structures and methods for fabricating the same.
Description of the Related Art
Generally, capacitor structures are used in electrical passive elements in semiconductor integrated circuits (IC), such as radio frequency circuits and mixed signal circuits. The types of conventional capacitor structures used in semiconductor integrated circuits include metal-insulator-semiconductor (MIS) capacitors, PN junction capacitors, and polysilicon-insulator-polysilicon (PIP) capacitors.
However, conventional capacitor structures use semiconductor layers (such as polysilicon) as capacitance electrodes, and thus traditional capacitor structures have high serial resistances and have the disadvantage of being less stable in high-frequency circuits. Moreover, during operation, the electrodes of PN junction capacitors generate depletion layers that results in limited frequency characteristics. Compared to those traditional capacitors, MIM capacitor structures can provide lower serial resistance and low power dissipation characteristics, and thus MIM capacitor structures are suitable for today's mixed signal circuit and high-frequency circuit applications. In addition, MIM capacitor structures can be formed during the formation of the metal interconnections in semiconductor fabrication process, which reduces the difficulty and complexity of integrating capacitor structures into the front-end-of-line (FEOL) process of complementary metal oxide semiconductors (CMOS).
Semiconductor integrated circuits have undergone rapid development in order to scale down the dimensions of semiconductor elements. However, in the continuously shrinking areas, MIM capacitance structures are required to maintain high capacitance, and therefore the processes for forming MIM capacitance structures also face various new challenges.